The present invention relates to liquid passage switching devices. More particularly, the invention relates to a liquid passage switching device in which the liquid passage switching operation is carried out in a liquid in such a manner as to prevent the mixing of bubbles in the liquid.
In the field of photographic photosensitive material manufacture, it is often necessary to provide for switching of liquid passages to deliver liquids for the preparation of photographic emulsions. In such an operation, it is essential that no bubbles be mixed into the liquids to be delivered because, if only a single bubble is mixed in the prepared photographic emulsion, the bubble will cause a serious defect in quality in the finished photographic product.
However, the above-described requirement is not always satisfied by conventional liquid passage switching devices. In addition, conventional devices are disadvantageous in that bubbles are liable to mix into the liquid to be delivered and it is rather difficult to clean a conventional device.
A liquid passage switching device called "a ball valve" as shown in FIG. 1 is a well-known device of this general type. In this device, the passages 1, 2 and 3 are switched by turning a ball 4 which is rotatably provided in a housing 7 through predetermined angles. The device is disadvantageous in the following points. There are small gaps 5, 5' and 5" between the ball 4 and the housing 7. Therefore, as the ball 4 is turned, the gas contained in the small gaps is brought into the passages 1, 2 and 3 as a result of which the gas is mixed into the liquids. In addition, when the liquids are switched, the remaining old liquid has a tendency to stick to packings 6, 6' and 6" provided in the device making it difficult to sufficiently clean the valve.
Japanese Published Patent Application No. 1089/1975 discloses a liquid passage switching device in which, as shown in FIG. 2, a U-shaped connecting tube 8 is rotatable in the directions of the arrows by an actuator. A plurality of passages 9 whose openings are radially arranged are switched by moving the connecting tube 8 step by step. This conventional device is also disadvantageous in that, as the connecting tube 8 must be disconnected from a passage to switch the passages, the mixing of gases is unavoidably caused as in the above-described device and the liquid can leak to the outside.
Accordingly, an object of the invention is to provide a liquid passage switching device in which all of the abovedescribed drawbacks accompanying a conventional liquid passage switching device have been eliminated, the mixing of gases into the liquid during switching operations is eliminated, and cleaning can be readily achieved.